A known circuit arrangement for monitoring the state of a thyristor is shown in "etz", No. 25, Vol. 102, December 1981, on page 1341f in FIG. 7. The known circuit arrangement forms an integral part of the circuitry which is otherwise associated with the thyristor. The circuitry has a power supply of its own for supplying it with current from an auxiliary power output circuit which is connected in series with a damping resistor and a damping capacitor parallel to the thyristor. For monitoring the thyristor, the circuitry contains a signal transmitting device having an ohmic voltage divider connected in parallel to the thyristor. The tap of the voltage divider is connected to a signal processing circuit and then to a light emitting diode which emits light signals when addressed. The light signals are transmitted to an evaluating device via a light guide.